EP0130865B1 - Apparatus for making a single crystal - Google Patents

Apparatus for making a single crystal Download PDF

Info

Publication number
EP0130865B1
EP0130865B1 EP84401103A EP84401103A EP0130865B1 EP 0130865 B1 EP0130865 B1 EP 0130865B1 EP 84401103 A EP84401103 A EP 84401103A EP 84401103 A EP84401103 A EP 84401103A EP 0130865 B1 EP0130865 B1 EP 0130865B1
Authority
EP
European Patent Office
Prior art keywords
crucible
thermally conductive
heating means
heating
conductive means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84401103A
Other languages
German (de)
French (fr)
Other versions
EP0130865A1 (en
Inventor
Bernard Ferrand
Yves Grange
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commissariat a lEnergie Atomique CEA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP0130865A1 publication Critical patent/EP0130865A1/en
Application granted granted Critical
Publication of EP0130865B1 publication Critical patent/EP0130865B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/003—Heating or cooling of the melt or the crystallised material
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/002—Crucibles or containers for supporting the melt
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/12—Halides
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/90—Apparatus characterized by composition or treatment thereof, e.g. surface finish, surface coating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/901—Levitation, reduced gravity, microgravity, space
    • Y10S117/902—Specified orientation, shape, crystallography, or size of seed or substrate
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1092—Shape defined by a solid member other than seed or product [e.g., Bridgman-Stockbarger]

Definitions

  • the present invention relates to a device for producing a single crystal. It applies in particular to the production of single crystals which can be used as scintillators and in particular to the production of single crystals of barium fluoride BaF 2 .
  • the material to be crystallized is placed in a crucible which is moved in a low temperature gradient, from a high temperature zone to a low temperature zone.
  • the weakness of the temperature gradient makes it necessary to purify the material beforehand, which is generally carried out using the method known as "zone fusion".
  • zone fusion the method known as "zone fusion"
  • only a portion of an ingot of the material to be purified is heated, thus forming a thin molten layer and this layer is then made to move from one end of the ingot to the other, the impurities contained in this ingot then being driven towards one end of it.
  • This operation must be repeated several times to obtain a very pure material.
  • the use of a very steep thermal gradient causes the ingot to break into several pieces which are unusable in practice given their small dimensions and to which the BRIDGMAN method is then applied to obtain a monocrystal of suitable size.
  • the technique associating the zone fusion method with the BRIDGMAN method has drawbacks: it is a long and complex technique which requires a lot of handling of the material to be crystallized, which increases the risks of pollution thereof, pollution which is of course to be avoided, especially in the case of crystals intended for the production of scintillators.
  • the subject of the present invention is precisely a device for producing a single crystal, which does not have the drawbacks of the previously mentioned technique, in particular in that it is simpler, makes it possible to obtain growth rates of single crystals quite high, of the order of 2 to 10 mm / hour for example, requires very little manipulation of the material to be crystallized and therefore avoids any pollution thereof.
  • it is completely automated and allows custom crystals to be obtained, individually or in several copies at the same time, these crystals being able to also have all the desired shapes (cylindrical, parallelepiped, etc.). .
  • the heating means are designed to cause an abrupt decrease in temperature of the material heated by them when it is extracted therefrom thanks to said displacement means, the thermally conductive means is provided to control this decrease in temperature of the material melted by the heating means , the relative displacement means are provided to subject the material to a controlled temperature gradient and to obtain crystallization of the material, the latter then being slowly cooled to room temperature.
  • slow cooling is meant cooling not exceeding a few hundred degrees Celsius per hour, for example cooling of the order of 50 to 100 ° C / h.
  • rupt decrease in temperature is meant a decrease of the kind that is achieved in the zone fusion method, known in the state of the art.
  • thermally conductive means can be moved relative to the heating means or, on the contrary. these can be moved relative to the thermally conductive means.
  • the material is therefore melted in the heating means and then, by displacement, emerges at one end thereof. At this end, the material undergoes a temperature decrease and there appears a liquid-solid interface in the material.
  • the decrease in temperature is strong enough to cause a rejection of all the impurities of the material in its liquid part and therefore to purify the latter, and sufficiently attenuated by the thermally conductive means to allow continuous monocrystalline growth of the material, as and as it emerges from the heating means, this monocrystalline growth being initiated by the end of the material, which leaves the heating means first.
  • the present invention therefore corresponds to an intermediate technique between the BRIDGMAN method and the zone fusion method, while giving both the results which these two methods provide, namely the purification of the material and the obtaining of a single crystal. of suitable size of this material.
  • the device which is the subject of the invention, it comprises several crucibles, the thermally conductive means comprises a recess and the crucibles are arranged symmetrically around this recess. This avoids local overheating of the thermally conductive means.
  • the thermally conductive means and each crucible are made of purified graphite.
  • the heating means comprise high frequency inductor windings. Instead, they could have resistive windings heating by the Joule effect, but the resulting heating would then be less homogeneous as a result of a greater radial gradient.
  • the device which is the subject of the invention further comprises means for circulating a chemically inert gas, so as to produce the single crystal in a chemically inert atmosphere.
  • These heating means 3 comprise, here, essentially, around a quartz tube 6 of axis Z, arranged vertically, high frequency inductor windings 7 which surround only a portion of the tube 6 and which are supplied by a generator. high frequency current 8.
  • the upper (respectively lower) end of the tube 6 is provided with an O-ring 9 (respectively 10) and closed by a plug (respectively 12) threaded on the outside and in contact with one side of the O-ring, and by a ring 13 (respectively 14) threaded inside and in contact with the other side of the O-ring, the plug being screwed into the ring so as to compress the seal.
  • each plug 11 or 12 is hollowed out so as to allow the circulation of a cooling fluid introduced by a pipe 15a or 16a inside the plug 11 or 12 and evacuated by a pipe 15b or 16b of inside said plug.
  • a circulation of a chemically inert gas such as argon is established inside the tube 6.
  • the argon is introduced into the latter by a conduit 17 passing through the lower plug 12 and evacuated from the tube 6 by a conduit 18 passing through the upper plug 11 and leading to pumping means not shown.
  • the argon Prior to its introduction into the tube 6, the argon is freed from all traces of water by, for example, circulating it in a resistive oven 19 communicating with the conduit 17 provided for the introduction of the argon into the tube 6, the furnace 19 containing pieces 20 of the material sold under the name of TEFLON which, when heated, decomposes to give carbon tetrafluoride which fixes the water molecules.
  • the displacement means 4 comprise a rod 21 which passes through the lower plug 12 and which is vertically movable in the tube 6 along the axis Z, this rod 21 being controlled by a translation mechanism 22.
  • the thermally conductive means 2 is designed to be vertically movable along the axis Z in the tube 6 and comprises an upper part 23 extended below by an appendage 24 provided at its base with a housing 25 in which is fixed the rod 21.
  • the upper part 23 of the thermally means conductor 2 comprises several parallel and vertical housings 26 which open from the top of this upper part 23 and which are designed to receive crucibles 27 each intended to contain the material to be crystallized 28.
  • each crucible has, in known manner, a substantially conical tapered shape, conducive to the formation of a monocrystalline germ of the material contained in the crucible, when this material, melted in the heating means, solidifies out of those -this. This is how the bottom of each crucible constitutes said crystallization means 5.
  • the assembly constituted by the crucible holder 2 and by the crucibles 27 containing the material to be crystallized, so that said assembly is brought to a higher temperature, for example 20 ° C., than the melting temperature of the material considered and said assembly is maintained in the heating means for a sufficient time, around 1 hour per example, to have good temperature uniformity in the assembly in question.
  • the material is thus in the molten state.
  • the single crystals of the material are produced and it is then cooled slowly, with a speed of the order of 50 to 100 ° C / hour for example, the assembly constituted by the crucible holder 2, the crucibles 27 and the material which these contain, by acting on the power of the high frequency generator 8, until said assembly reaches ambient temperature (of the order 20 ° C).
  • the high frequency generator 8 and the resistive furnace 19 are then stopped and the single crystals are extracted from the crucibles 27. (These single crystals are in the form of ingots which must then be cut off the upper end in which the impurities are then initially concentrated. distributed in the material).
  • This material is subject, under excitation, to a light emission which has a slow component and a fast component, and must, to constitute a good scintillator material, be purified so as to reduce the defects of its crystal lattice, to reinforce the intensity of the fast component.
  • the barium fluoride is then introduced into the crucibles 27, for example in the form of a powder.
  • the assembly constituted by the crucible holder, the crucibles and the barium fluoride contained in them is brought by the heating means 3 to temperatures of around 1380 ° C and using a speed of translation of the crucible holder, between 1 and 10 mm per hour. With three crucibles for example, a speed of the order of 5 mm per hour is suitable.
  • the upper part 23 of the crucible holder 2 may have a recess 29 at its center, the housings 26 provided for receiving the crucibles 27 then being distributed symmetrically around said recess 29, as seen in Figures 2b and 2d.
  • the recess 29 makes it possible to have better temperature uniformity, avoiding overheating in the center of the part 23.
  • the different possible shapes for the single crystals to be produced can cause a distribution. non-uniform temperature in each cross section of these single crystals. This can easily be compensated for by a modification of the shape and / or of the nature of the crucible holder 2 and / or of the type of high frequency heating (skin effect). By doing so, and thanks to high frequency heating (that is to say by high frequency inductor windings), the material to be crystallized can be heated uniformly at all points whatever its shape. Resistive heating (carried out using resistive windings heating by Joule effect) is possible but is less homogeneous than high frequency heating for the assembly constituted by the crucible holder and the crucibles containing the material to be crystallized.
  • the initial position of the crucible holder 2 is such that the material to be crystallized is initially included in the range delimited by the windings 7.
  • the initial position of the crucible holder could be higher in the tube 6, the material to be crystallized then being initially outside the heating range delimited by the windings 7, but the time to develop the crystals would then be higher.
  • FIGS. 3a, 3b and 3c graphs are given giving the temperature T as a function of the position on the axis Z, for a material to be crystallized to which the BRIDGMAN method is applied respectively (FIG. 3a), the method of zone fusion ( Figure 3b) and a method using the device of the invention ( Figure 3c).
  • the thermal gradient undergone by the material in the present invention is intermediate between the thermal gradient which it would undergo in the BRIDGMAN method and the thermal gradient which it would undergo in the zone fusion method.
  • a single crystal of barium fluoride produced with the invention has a light emission whose fast component has an intensity which is more reinforced compared to the slow component than the fast component of a single crystal of barium fluoride obtained by applying successively the zone fusion method and the BRIDGMAN method for barium fluoride.

Description

La présente invention concerne un dispositif d'élaboration d'un monocristal. Elle s'applique notamment à l'élaboration de monocristaux utilisables comme scintillateurs et en particulier à l'élaboration de monocristaux de fluorure de baryum BaF2.The present invention relates to a device for producing a single crystal. It applies in particular to the production of single crystals which can be used as scintillators and in particular to the production of single crystals of barium fluoride BaF 2 .

On connaît des techniques d'élaboration de monocristaux, la plus utilisée étant la méthode de BRIDGMAN. Selon cette méthode, le matériau à cristalliser est disposé dans un creuset que l'on déplace dans un faible gradient de température, d'une zone de haute température vers une zone de basse température. La faiblesse du gradient de température rend indispensable la purification préalable du matériau, ce qui est généralement réalisé a l'aide de la méthode connue sous le nom de « fusion de zone ». Selon cette méthode, on chauffe une partie seulement d'un lingot du matériau à purifier, formant ainsi une mince couche en fusion et l'on fait ensuite se déplacer cette couche d'une extrémité du lingot à l'autre, les impuretés contenues dans ce lingot étant alors entraînées vers une extrémité de celui-ci. Il faut recommencer plusieurs fois cette opération pour obtenir un matériau très pur. En outre, l'utilisation d'un gradient thermique très abrupt provoque la cassure du lingot en plusieurs morceaux qui sont inutilisables en pratique étant donné leurs petites dimensions et auxquels on applique ensuite la méthode de BRIDGMAN pour obtenir un monocristal de taille convenable.Techniques for developing single crystals are known, the most used being the BRIDGMAN method. According to this method, the material to be crystallized is placed in a crucible which is moved in a low temperature gradient, from a high temperature zone to a low temperature zone. The weakness of the temperature gradient makes it necessary to purify the material beforehand, which is generally carried out using the method known as "zone fusion". According to this method, only a portion of an ingot of the material to be purified is heated, thus forming a thin molten layer and this layer is then made to move from one end of the ingot to the other, the impurities contained in this ingot then being driven towards one end of it. This operation must be repeated several times to obtain a very pure material. In addition, the use of a very steep thermal gradient causes the ingot to break into several pieces which are unusable in practice given their small dimensions and to which the BRIDGMAN method is then applied to obtain a monocrystal of suitable size.

La technique associant la méthode de fusion de zone a la méthode de BRIDGMAN présente des inconvénients : c'est une technique longue et complexe qui nécessite beaucoup de manipulations du matériau à cristalliser, ce qui augmente les risques de pollution de celui-ci, pollution qui est bien entendu à éviter, surtout dans le cas des cristaux destinés à la réalisation de scintillateurs.The technique associating the zone fusion method with the BRIDGMAN method has drawbacks: it is a long and complex technique which requires a lot of handling of the material to be crystallized, which increases the risks of pollution thereof, pollution which is of course to be avoided, especially in the case of crystals intended for the production of scintillators.

La présente invention a justement pour objet un dispositif d'élaboration d'un monocristal, qui ne présente pas les inconvénients de la technique précédemment rappelée, notamment en ce qu'il est plus simple, permet d'obtenir des vitesses de croissance de monocristaux assez élevées, de l'ordre de 2 à 10 mm/heure par exemple, ne nécessite que très peu de manipulation du matériau à cristalliser et évite donc toute pollution de celui-ci. En outre, il est complètement automatisa- ble et permet d'obtenir des cristaux sur mesure, à l'unité ou en plusieurs exemplaires à la fois, ces cristaux pouvant de plus présenter toutes les formes souhaitées (cylindrique, parallélépipédique, ...).The subject of the present invention is precisely a device for producing a single crystal, which does not have the drawbacks of the previously mentioned technique, in particular in that it is simpler, makes it possible to obtain growth rates of single crystals quite high, of the order of 2 to 10 mm / hour for example, requires very little manipulation of the material to be crystallized and therefore avoids any pollution thereof. In addition, it is completely automated and allows custom crystals to be obtained, individually or in several copies at the same time, these crystals being able to also have all the desired shapes (cylindrical, parallelepiped, etc.). .

On connaît déjà, par le document GB-A-923241, une technique de fabrication de monocristaux, selon laquelle on introduit les composants des monocristaux désirés dans un creuset présentant une fusion pâteuse. Le creuset est placé à son tour dans une enveloppe en graphite. On porte rapidement l'ensemble à une température de fusion des composants afin de ne produire qu'un minimum de décomposition de ces derniers. Le creuset se plaque contre l'enveloppe en graphite et les monocristaux sont obtenus par refroidissement sous gradient de température faible.Document GB-A-923241 already discloses a technique for manufacturing single crystals, according to which the components of the desired single crystals are introduced into a crucible having a pasty melting. The crucible is in turn placed in a graphite casing. The assembly is quickly brought to a melting point of the components so as to produce only a minimum of decomposition of the latter. The crucible is pressed against the graphite envelope and the single crystals are obtained by cooling under a low temperature gradient.

De façon précise, la présente invention a pour objet un dispositif d'élaboration d'un monocristal à partir d'un matériau apte à cristalliser, ce dispositif comprenant :

  • - au moins un creuset thermiquement conducteur, prévu pour recevoir le matériau,
  • - un moyen thermiquement conducteur apte à recevoir chaque creuset,
  • - des moyens de chauffage dudit moyen thermiquement conducteur et de chaque creuset contenant ledit matériau, ces moyens de chauffage ayant une longueur au moins égale à celle de chaque creuset, et
  • - des moyens de déplacement relatif dudit moyen thermiquement conducteur et de chaque creuset contenant ledit matériau par rapport auxdits moyens de chauffage ;
    • le moyen thermiquement conducteur comporte une partie supérieure, apte à recevoir chaque creuset, et une partie inférieure prolongeant inférieurement la partie supérieure et formant un appendice de cette partie supérieure, le fond de chaque creuset est de forme effilée, de façon à constituer des moyens de cristallisation aptes à provoquer la cristallisation d'une extrémité dudit matériau fondu dans les moyens de chauffage, ces moyens de chauffage permettant la sortie du moyen thermiquement conducteur par le bas desdits moyens de chauffage, et l'appendice est disposé de façon à modifier le gradient thermique subi par le matériau lors du déplacement relatif.
Specifically, the subject of the present invention is a device for producing a single crystal from a material capable of crystallizing, this device comprising:
  • - at least one thermally conductive crucible, designed to receive the material,
  • - a thermally conductive means capable of receiving each crucible,
  • means for heating said thermally conductive means and each crucible containing said material, these heating means having a length at least equal to that of each crucible, and
  • - means for relative displacement of said thermally conductive means and of each crucible containing said material with respect to said heating means;
    • the thermally conductive means comprises an upper part, capable of receiving each crucible, and a lower part extending below the upper part and forming an appendage of this upper part, the bottom of each crucible is of tapered shape, so as to constitute means of crystallization capable of causing the crystallization of one end of said molten material in the heating means, these heating means allowing the exit of the thermally conductive means from the bottom of said heating means, and the appendix is arranged so as to modify the gradient thermal undergone by the material during relative displacement.

Les moyens de chauffage sont conçus pour provoquer une diminution abrupte de température du matériau chauffé par eux lorsqu'il en est extrait grâce auxdits moyens de déplacement, le moyen thermiquement conducteur est prévu pour contrôler cette diminution de température du matériau fondu par les moyens de chauffage, les moyens de déplacement relatif sont prévus pour soumettre le matériau à un gradient de température contrôlé et pour obtenir une cristallisation du matériau, celui-ci étant ensuite lentement refroidi jusqu'à la température ambiante.The heating means are designed to cause an abrupt decrease in temperature of the material heated by them when it is extracted therefrom thanks to said displacement means, the thermally conductive means is provided to control this decrease in temperature of the material melted by the heating means , the relative displacement means are provided to subject the material to a controlled temperature gradient and to obtain crystallization of the material, the latter then being slowly cooled to room temperature.

Par «refroidissement lent», on entend un refroidissement ne dépassant pas quelques centaines de degrés Celsius par heure, par exemple un refroidissement de l'ordre de 50 à 100°C/h.By "slow cooling" is meant cooling not exceeding a few hundred degrees Celsius per hour, for example cooling of the order of 50 to 100 ° C / h.

Par « diminution abrupte de température », on entend une diminution du genre de celle que l'on réalise dans la méthode de fusion de zone, connue dans l'état de la technique.By "abrupt decrease in temperature" is meant a decrease of the kind that is achieved in the zone fusion method, known in the state of the art.

Bien entendu, le moyen thermiquement conducteur peut être déplacé par rapport aux moyens de chauffage ou, au contraire. ces derniers peuvent être déplacés par rapport au moyen thermiquement conducteur.Of course, the thermally conductive means can be moved relative to the heating means or, on the contrary. these can be moved relative to the thermally conductive means.

Dans la présente invention, le moyen thermiquement conducteur est fondamental : il permet par conduction thermique, d'homogénéiser la température du matériau et d'atténuer la diminution abrupte de température que l'on peut également appeler « gradient thermique abrupt ». Le gradient thermique éprouvé par le matériau peut être modifié à volonté en modifiant la forme et/ou la nature du moyen thermiquement conducteur.In the present invention, the thermally conductive means is fundamental: it allows by thermal conduction, to homogenize the temperature of the material and to attenuate the abrupt reduction of temperature which one can also call “abrupt thermal gradient”. The thermal gradient experienced by the material can be modified at will by modifying the shape and / or the nature of the thermally conductive means.

Selon la présente invention, le matériau est donc fondu dans les moyens de chauffage puis, par déplacement, émerge à une extrémité de ceux-ci. En cette extrémité, le matériau subit une diminution de température et il apparaît une interface liquide-solide dans le matériau. La diminution de température est suffisamment forte pour entraîner un rejet de toutes les impuretés du matériau dans sa partie liquide et donc pour purifier celui-ci, et suffisamment atténuée par le moyen thermiquement conducteur pour permettre une croissance monocristalline continue du matériau, au fur et à mesure qu'il émerge des moyens de chauffage, cette croissance monocristalline étant initiée par l'extrémité du matériau, sortie la première des moyens de chauffage.According to the present invention, the material is therefore melted in the heating means and then, by displacement, emerges at one end thereof. At this end, the material undergoes a temperature decrease and there appears a liquid-solid interface in the material. The decrease in temperature is strong enough to cause a rejection of all the impurities of the material in its liquid part and therefore to purify the latter, and sufficiently attenuated by the thermally conductive means to allow continuous monocrystalline growth of the material, as and as it emerges from the heating means, this monocrystalline growth being initiated by the end of the material, which leaves the heating means first.

La présente invention correspond donc à une technique intermédiaire entre la méthode de BRIDGMAN et la méthode de fusion de zone, tout en donnant à la fois les résultats que procurent ces deux méthodes, à savoir la purification du matériau et l'obtention d'un monocristal de taille convenable de ce matériau.The present invention therefore corresponds to an intermediate technique between the BRIDGMAN method and the zone fusion method, while giving both the results which these two methods provide, namely the purification of the material and the obtaining of a single crystal. of suitable size of this material.

Selon une caractéristique particulière du dispositif objet de l'invention, celui-ci comporte plusieurs creusets, le moyen thermiquement conducteur comporte un évidement et les creusets sont disposés symétriquement autour de cet évidement. On évite ainsi une surchauffe locale du moyen thermiquement conducteur.According to a particular characteristic of the device which is the subject of the invention, it comprises several crucibles, the thermally conductive means comprises a recess and the crucibles are arranged symmetrically around this recess. This avoids local overheating of the thermally conductive means.

Selon une autre caractéristique préférée du dispositif objet de l'invention, le moyen thermiquement conducteur et chaque creuset sont en graphite purifié.According to another preferred characteristic of the device which is the subject of the invention, the thermally conductive means and each crucible are made of purified graphite.

Selon une autre caractéristique préférée, les moyens de chauffage comportent des enroulements inducteurs à haute fréquence. Au lieu de cela, ils pourraient comporter des enroulements résistifs chauffant par effet Joule, mais le chauffage résultant serait alors moins homogène par suite d'un gradient radial plus important.According to another preferred characteristic, the heating means comprise high frequency inductor windings. Instead, they could have resistive windings heating by the Joule effect, but the resulting heating would then be less homogeneous as a result of a greater radial gradient.

Selon une autre caractéristique particulière, l'ensemble constitué par le moyen thermiquement conducteur, chaque creuset et le matériau, est placé dans une enceinte l'isolant de l'atmosphère extérieure.According to another particular characteristic, the assembly constituted by the thermally conductive means, each crucible and the material, is placed in an enclosure isolating it from the external atmosphere.

Enfin, de préférence, le dispositif objet de l'invention comporte en outre des moyens de circulation d'un gaz chimiquement inerte, de manière à élaborer le monocristal en atmosphère chimiquement inerte.Finally, preferably, the device which is the subject of the invention further comprises means for circulating a chemically inert gas, so as to produce the single crystal in a chemically inert atmosphere.

L'invention sera mieux comprise à la lecture de la description qui suit, d'exemples de réalisation donnés à titre indicatif et nullement limitatif, en référence aux dessins annexés sur lesquels :

  • - la figure 1 est une vue schématique d'un mode de réalisation particulier du dispositif objet de l'invention,
  • - les figures 2a à 2d sont des coupes transversales schématiques de modes de réalisation particuliers du moyen thermiquement conducteur et des creusets utilisés dans l'invention, et
  • - les figures 3a à 3c sont des graphiques montrant les différences entre l'invention et les méthodes de BRIDGMAN et de fusion de zone.
The invention will be better understood on reading the description which follows, of exemplary embodiments given by way of indication and in no way limiting, with reference to the appended drawings in which:
  • FIG. 1 is a schematic view of a particular embodiment of the device which is the subject of the invention,
  • FIGS. 2a to 2d are schematic cross-sections of particular embodiments of the thermally conductive means and of the crucibles used in the invention, and
  • - Figures 3a to 3c are graphs showing the differences between the invention and the BRIDGMAN and zone fusion methods.

Sur la figure 1, on a représenté schématiquement un mode de réalisation particulier du dispositif objet de l'invention. Il comprend essentiellement :

  • - un moyen thermiquement conducteur 2 apte à contenir au moins un creuset 27 rempli du matériau à cristalliser 28,
  • - des moyens de chauffage 3,
  • - des moyens 4 de déplacement du moyen thermiquement conducteur 2 par rapport aux moyens de chauffage 3, et
  • - des moyens de cristallisation 5, aptes à déclencher la cristallisation du matériau lorsqu'il est extrait des moyens de chauffage 3.
In Figure 1, there is shown schematically a particular embodiment of the device object of the invention. It basically includes:
  • a thermally conductive means 2 capable of containing at least one crucible 27 filled with the material to be crystallized 28,
  • - heating means 3,
  • means 4 for moving the thermally conductive means 2 relative to the heating means 3, and
  • - crystallization means 5, capable of triggering the crystallization of the material when it is extracted from the heating means 3.

Ces moyens de chauffage 3 comportent, ici, essentiellement, autour d'un tube en quartz 6 d'axe Z, disposé verticalement, des enroulements inducteurs à haute fréquence 7 qui entourent seulement une portion du tube 6 et qui sont alimentés par un générateur de courant à haute fréquence 8.These heating means 3 comprise, here, essentially, around a quartz tube 6 of axis Z, arranged vertically, high frequency inductor windings 7 which surround only a portion of the tube 6 and which are supplied by a generator. high frequency current 8.

L'extrémité supérieure (respectivement inférieure) du tube 6 est munie d'un joint torique 9 (respectivement 10) et obturée par un bouchon (respectivement 12) fileté à l'extérieur et en contact avec un côté du joint torique, et par une bague 13 (respectivement 14) filetée à l'intérieur et en contact avec l'autre côté du joint torique, le bouchon étant vissé dans la bague de façon à comprimer le joint.The upper (respectively lower) end of the tube 6 is provided with an O-ring 9 (respectively 10) and closed by a plug (respectively 12) threaded on the outside and in contact with one side of the O-ring, and by a ring 13 (respectively 14) threaded inside and in contact with the other side of the O-ring, the plug being screwed into the ring so as to compress the seal.

L'intérieur 15 ou 16 de chaque bouchon 11 ou 12 est évidé de manière à permettre la circulation d'un fluide réfrigérant introduit par un conduit 15a ou 16a à l'intérieur du bouchon 11 ou 12 et évacué par un conduit 15b ou 16b de l'intérieur dudit bouchon.The interior 15 or 16 of each plug 11 or 12 is hollowed out so as to allow the circulation of a cooling fluid introduced by a pipe 15a or 16a inside the plug 11 or 12 and evacuated by a pipe 15b or 16b of inside said plug.

En outre, on établit une circulation d'un gaz chimiquement inerte tel que l'argon, à l'intérieur du tube 6. L'argon est introduit dans ce dernier par un conduit 17 traversant le bouchon inférieur 12 et évacué du tube 6 par un conduit 18 traversant le bouchon supérieur 11 et conduisant à des moyens de pompage non représentés. Préalablement à son introduction dans le tube 6, l'argon est débarrassé de toute trace d'eau en le faisant par exemple circuler dans un four résistif 19 communiquant avec le conduit 17 prévu pour l'introduction de l'argon dans le tube 6, le four 19 contenant des morceaux 20 du matériau commercialisé sous le nom de TEFLON qui, chauffé, se décompose pour donner du tétrafluorure de carbone qui fixe les molécules d'eau.In addition, a circulation of a chemically inert gas such as argon is established inside the tube 6. The argon is introduced into the latter by a conduit 17 passing through the lower plug 12 and evacuated from the tube 6 by a conduit 18 passing through the upper plug 11 and leading to pumping means not shown. Prior to its introduction into the tube 6, the argon is freed from all traces of water by, for example, circulating it in a resistive oven 19 communicating with the conduit 17 provided for the introduction of the argon into the tube 6, the furnace 19 containing pieces 20 of the material sold under the name of TEFLON which, when heated, decomposes to give carbon tetrafluoride which fixes the water molecules.

Les moyens de déplacement 4 comportent une tige 21 qui traverse le bouchon inférieur 12 et qui est déplaçable verticalement dans le tube 6 suivant l'axe Z, cette tige 21 étant commandée par un mécanisme de translation 22.The displacement means 4 comprise a rod 21 which passes through the lower plug 12 and which is vertically movable in the tube 6 along the axis Z, this rod 21 being controlled by a translation mechanism 22.

Le moyen thermiquement conducteur 2 est conçu pour être déplaçable verticalement suivant l'axe Z dans le tube 6 et comporte une partie supérieure 23 prolongée inférieurement par un appendice 24 pourvu à sa base d'un logement 25 dans lequel est fixée la tige 21. La partie supérieure 23 du moyen thermiquement conducteur 2 comporte plusieurs logements 26 parallèles et verticaux qui débouchent du sommet de cette partie supérieure 23 et qui sont conçus pour recevoir des creusets 27 destinés à contenir chacun le matériau à cristalliser 28.The thermally conductive means 2 is designed to be vertically movable along the axis Z in the tube 6 and comprises an upper part 23 extended below by an appendage 24 provided at its base with a housing 25 in which is fixed the rod 21. The upper part 23 of the thermally means conductor 2 comprises several parallel and vertical housings 26 which open from the top of this upper part 23 and which are designed to receive crucibles 27 each intended to contain the material to be crystallized 28.

Le moyen thermiquement conducteur 2, que l'on peut maintenant appeler porte-creusets, est destiné à être déplacé dans le tube 6 d'une position haute A dans laquelle la totalité du matériau contenu dans les différents creusets 27 se trouve à l'intérieur du domaine délimité par les enroulements 7, ceux-ci ayant une longueur prévue à cet effet, à une position basse B dans laquelle seul le sommet du porte-creusets 2 se trouve encore à l'intérieur dudit domaine.The thermally conductive means 2, which can now be called crucible carrier, is intended to be moved in the tube 6 from a high position A in which all of the material contained in the various crucibles 27 is inside. of the area delimited by the windings 7, these having a length provided for this purpose, in a low position B in which only the top of the crucible holder 2 is still inside said area.

De préférence, le porte-creusets 2 et les creusets 27 sont en graphite dit « nucléaire ».Preferably, the crucible holder 2 and the crucibles 27 are made of so-called “nuclear” graphite.

Le fond de chaque creuset présente, de façon connue, une forme effilée sensiblement conique, propice à la formation d'un germe monocristallin du matériau contenu dans le creuset, lorsque ce matériau, fondu dans les moyens de chauffage, se solidifie en sortant de ceux-ci. C'est ainsi que le fond de chaque creuset constitue lesdits moyens de cristallisation 5.The bottom of each crucible has, in known manner, a substantially conical tapered shape, conducive to the formation of a monocrystalline germ of the material contained in the crucible, when this material, melted in the heating means, solidifies out of those -this. This is how the bottom of each crucible constitutes said crystallization means 5.

On va maintenant expliquer le procédé d'élaboration de monocristaux mis en oeuvre dans le dispositif que l'on vient de décrire en référence à la figure 1 : les creusets 27, remplis du matériau à cristalliser, sont mis en place dans le porte-creusets 2, celui-ci étant en position haute dans le tube 6. On fait alors circuler l'argon dans ce dernier avec un débit de l'ordre de 4 litres par minute par exemple et l'on met en marche le four résistif 19. Lorsque celui-ci a atteint une température de l'ordre de 460 °C (température permettant la décomposition du TEFLON contenu dans ce four), on procède à la montée en température de l'ensemble constitué par le porte-creusets 2 et par les creusets 27 contenant le matériau à cristalliser, de manière que ledit ensemble se trouve porté à une température supérieure, de 20 °C par exemple, à la température de fusion du matériau considéré et l'on maintient ledit ensemble dans les moyens de chauffage pendant un temps suffisant, de l'ordre de 1 heure par exemple, pour avoir une bonne homogénéité de température dans l'ensemble en question. Le matériau se trouve ainsi à l'état fondu.We will now explain the process for producing single crystals used in the device that has just been described with reference to FIG. 1: the crucibles 27, filled with the material to be crystallized, are placed in the crucible holder 2, the latter being in the high position in the tube 6. Argon is then circulated in the latter with a flow rate of the order of 4 liters per minute for example and the resistive oven 19 is started up. When the latter has reached a temperature of the order of 460 ° C. (temperature allowing the decomposition of the TEFLON contained in this oven), the assembly constituted by the crucible holder 2 and by the crucibles 27 containing the material to be crystallized, so that said assembly is brought to a higher temperature, for example 20 ° C., than the melting temperature of the material considered and said assembly is maintained in the heating means for a sufficient time, around 1 hour per example, to have good temperature uniformity in the assembly in question. The material is thus in the molten state.

On opère alors une translation du porte-creusets vers le bas, la vitesse de translation étant fonction du matériau à cristalliser, de la forme du porte-creusets 2 et du nombre de creusets utilisés. Ainsi utilise-t-on une vitesse plus grande avec un seul creuset qu'avec plusieurs.There is then a downward translation of the crucible holder, the translation speed being a function of the material to be crystallized, the shape of the crucible holder 2 and the number of crucibles used. So we use a higher speed with a single crucible than with several.

Lorsque les creusets quittent le domaine de chauffage délimité par les enroulements 7, le matériau se trouvant au fond des creusets subit un gradient thermique important, mais atténué par le porte-creusets 2, et forme alors un germe monocristallin. La descente du porte-creusets 2 se poursuivant, la formation d'un monocristal dans chaque creuset continue, la variation de température subie par le matériau quittant le domaine de chauffage étant néanmoins suffisamment forte pour que les impuretés contenues dans le matériau diffusent vers le haut de celui-ci.When the crucibles leave the heating domain delimited by the windings 7, the material located at the bottom of the crucibles undergoes a significant thermal gradient, but attenuated by the crucible holder 2, and then forms a monocrystalline germ. The descent of the crucible holder 2 continues, the formation of a single crystal in each crucible continues, the temperature variation undergone by the material leaving the heating domain being nevertheless sufficiently strong for the impurities contained in the material to diffuse upwards of it.

En fin de translation, correspondant à la position basse B du porte-creusets 2, les monocristaux du matériau se trouvent élaborés et l'on refroidit alors lentement, avec une vitesse de l'ordre de 50 à 100°C/heure par exemple, l'ensemble constitué par le porte-creusets 2, les creusets 27 et le matériau que ceux-ci contiennent, en agissant sur la puissance du générateur haute fréquence 8, jusqu'à ce que ledit ensemble atteigne la température ambiante (de l'ordre de 20 °C). Le générateur haute fréquence 8 et le four résistif 19 sont alors arrêtés et les monocristaux sont extraits des creusets 27. (Ces monocristaux se présentent sous la forme de lingots dont on doit ensuite couper l'extrémité supérieure en laquelle se trouvent alors concentrées les impuretés initialement réparties dans le matériau).At the end of translation, corresponding to the low position B of the crucible holder 2, the single crystals of the material are produced and it is then cooled slowly, with a speed of the order of 50 to 100 ° C / hour for example, the assembly constituted by the crucible holder 2, the crucibles 27 and the material which these contain, by acting on the power of the high frequency generator 8, until said assembly reaches ambient temperature (of the order 20 ° C). The high frequency generator 8 and the resistive furnace 19 are then stopped and the single crystals are extracted from the crucibles 27. (These single crystals are in the form of ingots which must then be cut off the upper end in which the impurities are then initially concentrated. distributed in the material).

Il est à noter que l'automatisme du dispositif selon l'invention représenté sur la figure 1 est total dès la mise en marche de la translation du porte-creusets 2.It should be noted that the automation of the device according to the invention shown in FIG. 1 is complete as soon as the translation of the crucible holder 2 starts.

Le procédé expliqué ci-dessus est tout particulièrement applicable à la fabrication de monocristaux de fluorure de baryum. Ce matériau est sujet, sous excitation, à une émission de lumière qui présente une composante lente et une composante rapide, et doit, pour constituer un matériau scintillateur de bonne qualité, être purifié de façon à réduire les défauts de son réseau cristallin, pour renforcer l'intensité de la composante rapide.The process explained above is particularly applicable to the manufacture of barium fluoride single crystals. This material is subject, under excitation, to a light emission which has a slow component and a fast component, and must, to constitute a good scintillator material, be purified so as to reduce the defects of its crystal lattice, to reinforce the intensity of the fast component.

Le fluorure de baryum est alors introduit dans les creusets 27 par exemple sous forme de poudre. A titre indicatif et non limitatif, dans le cas du fluorure de baryum, l'ensemble constitué par le porte-creusets, les creusets et le fluorure de baryum contenu dans ceux-ci, est porté par les moyens de chauffage 3 à des températures de l'ordre de 1380 °C et l'on utilise une vitesse de translation du porte-creusets, comprise entre 1 et 10 mm par heure. Avec trois creusets par exemple, une vitesse de l'ordre de 5 mm par heure convient.The barium fluoride is then introduced into the crucibles 27, for example in the form of a powder. By way of indication and without limitation, in the case of barium fluoride, the assembly constituted by the crucible holder, the crucibles and the barium fluoride contained in them, is brought by the heating means 3 to temperatures of around 1380 ° C and using a speed of translation of the crucible holder, between 1 and 10 mm per hour. With three crucibles for example, a speed of the order of 5 mm per hour is suitable.

Il est à noter que le démoulage des monocristaux de fluorure de baryum obtenus est aisé, étant donné qu'un phénomène de retrait se produit pour ce matériau lors de sa cristallisation.It should be noted that the demolding of the single crystals of barium fluoride obtained is easy, since a shrinkage phenomenon occurs for this material during its crystallization.

Grâce à la présente invention, on peut élaborer simultanément plusieurs monocristaux et donner à ceux-ci des formes très variées. Il suffit pour cela de donner aux creusets la forme voulue. C'est ce que l'on a représenté sur les figures 2a à 2d sur lesquelles on voit des creusets 27 qui sont régulièrement positionnés dans des porte-creusets 2 et qui présentent des sections droites carrée, rectangulaire, triangulaire et elliptique. L'invention permet par exemple de réaliser des monocristaux de section droite carrée, de 26 mm de côté et de 120 mm de longueur, dans trois creusets maintenus dans un porte-creusets cylindrique de 130 mm de diamètre.Thanks to the present invention, several single crystals can be produced simultaneously and given to these very varied forms. It suffices to give the crucibles the desired shape. This is what is shown in Figures 2a to 2d in which we see crucibles 27 which are regularly positioned in crucible holders 2 and which have square, rectangular, triangular and elliptical cross sections. The invention makes it possible, for example, to produce single crystals of square cross section, 26 mm side and 120 mm length, in three crucibles held in a cylindrical crucible holder of 130 mm diameter.

Dans le cas où l'on utilise simultanément plusieurs creusets 27, la partie supérieure 23 du porte-creusets 2 peut comporter en son centre un évidement 29, les logements 26 prévus pour recevoir les creusets 27 étant alors répartis symétriquement autour dudit évidement 29, comme on le voit sur les figures 2b et 2d. L'évidement 29 permet d'avoir une meilleure homogénéité de température, en évitant une surchauffe au centre de la partie 23.In the case where several crucibles 27 are used simultaneously, the upper part 23 of the crucible holder 2 may have a recess 29 at its center, the housings 26 provided for receiving the crucibles 27 then being distributed symmetrically around said recess 29, as seen in Figures 2b and 2d. The recess 29 makes it possible to have better temperature uniformity, avoiding overheating in the center of the part 23.

Les différentes formes possibles pour les monocristaux à élaborer peuvent entraîner une réparti- . tion non uniforme de température dans chaque section transverse de ces monocristaux. Ceci peut être compensé aisément par une modification de la forme et/ou de la nature du porte-creusets 2 et/ou du type de chauffage par haute fréquence (effet de peau). En procédant ainsi, et grâce au chauffage par haute fréquence (c'est-à-dire par des enroulements inducteurs à haute fréquence), le matériau à cristalliser peut être chauffé uniformément en tous points quelle que soit sa forme. Un chauffage résistif (réalisé à l'aide d'enroulements résistifs chauffant par effet Joule) est possible mais est moins homogène qu'un chauffage haute fréquence pour l'ensemble constitué par le porte-creusets et les creusets contenant le matériau à cristalliser.The different possible shapes for the single crystals to be produced can cause a distribution. non-uniform temperature in each cross section of these single crystals. This can easily be compensated for by a modification of the shape and / or of the nature of the crucible holder 2 and / or of the type of high frequency heating (skin effect). By doing so, and thanks to high frequency heating (that is to say by high frequency inductor windings), the material to be crystallized can be heated uniformly at all points whatever its shape. Resistive heating (carried out using resistive windings heating by Joule effect) is possible but is less homogeneous than high frequency heating for the assembly constituted by the crucible holder and the crucibles containing the material to be crystallized.

On a indiqué plus haut que la position initiale du porte-creusets 2 est telle que le matériau à cristalliser se trouve au départ compris dans le domaine délimité par les enroulements 7. Bien entendu, la position initiale du porte-creusets pourrait être plus élevée dans le tube 6, le matériau à cristalliser se trouvant alors au départ en dehors du domaine de chauffage délimité par les enroulements 7, mais le temps pour élaborer les cristaux serait alors plus élevé.It was indicated above that the initial position of the crucible holder 2 is such that the material to be crystallized is initially included in the range delimited by the windings 7. Of course, the initial position of the crucible holder could be higher in the tube 6, the material to be crystallized then being initially outside the heating range delimited by the windings 7, but the time to develop the crystals would then be higher.

Sur les figures 3a, 3b et 3c, on a représenté des graphiques donnant la température T en fonction de la position sur l'axe Z, pour un matériau à cristalliser auquel on applique respectivement la méthode de BRIDGMAN (figure 3a), la méthode de fusion de zone (figure 3b) et un procédé utilisant le dispositif de l'invention (figure 3c).In FIGS. 3a, 3b and 3c, graphs are given giving the temperature T as a function of the position on the axis Z, for a material to be crystallized to which the BRIDGMAN method is applied respectively (FIG. 3a), the method of zone fusion (Figure 3b) and a method using the device of the invention (Figure 3c).

Dans la méthode de BRIDGMAN, le gradient thermique subi par le matériau à cristalliser est faible et il n'est pas du tout question d'utiliser un porte-creusets pour atténuer ce gradient. Dans la méthode de fusion de zone, le chauffage du matériau est très localisé, le gradient thermique que subit ce matériau est très brutal. Dans la présente invention, on utilise donc précisément un porte-creusets pour homogénéiser la température du matériau et pour atténuer le gradient thermique abrupt engendré par les moyens de chauffage, gradient qui produirait seulement un effet de purification du matériau s'il n'était pas atténué.In the BRIDGMAN method, the thermal gradient undergone by the material to be crystallized is low and there is no question of using a crucible holder to attenuate this gradient. In the zone fusion method, the heating of the material is very localized, the thermal gradient that this material undergoes is very brutal. In the present invention, therefore, a crucible holder is used precisely to homogenize the temperature of the material and to attenuate the abrupt thermal gradient generated by the heating means, a gradient which would only produce a material purification effect if it were not mitigated.

En d'autres termes, le gradient thermique subi par le matériau dans la présente invention, est intermédiaire entre le gradient thermique qu'il subirait dans la'méthode de BRIDGMAN et le gradient thermique qu'il subirait dans la méthode de fusion de zone.In other words, the thermal gradient undergone by the material in the present invention is intermediate between the thermal gradient which it would undergo in the BRIDGMAN method and the thermal gradient which it would undergo in the zone fusion method.

D'ailleurs, en réalisant par exemple un monocristal de fluorure de baryum avec le dispositif de l'invention, on obtient des résultats bien supérieurs à ceux que l'on obtient en appliquant d'abord la méthode de fusion de zone puis la méthode de BRIDGMAN au fluorure de baryum. En effet, un monocristal de fluorure de baryum réalisé avec l'invention présente une émission lumineuse dont la composante rapide a une intensité qui est plus renforcée par rapport à la composante lente que la composante rapide d'un monocristal de fluorure de baryum obtenu en appliquant successivement la méthode de fusion de zone et la méthode de BRIDGMAN audit fluorure de baryum.Moreover, by making, for example, a single crystal of barium fluoride with the device of the invention, results are obtained which are much higher than those obtained by first applying the zone fusion method and then the method of BRIDGMAN with barium fluoride. Indeed, a single crystal of barium fluoride produced with the invention has a light emission whose fast component has an intensity which is more reinforced compared to the slow component than the fast component of a single crystal of barium fluoride obtained by applying successively the zone fusion method and the BRIDGMAN method for barium fluoride.

Claims (8)

1. Apparatus for producing a monocrystal from a crystallizable material (28), said apparatus comprising at least one thermally conductive crucible (27) for receiving the material (28), a thermally conductive means (2) able to receive each crucible (27) and means (3) for heating the thermally conductive means (2) and each crucible (27) containing the material, said heating means having a length at least equal to that of each crucible, means (4) for the relative displacement of said thermally conductive means (2) and each crucible (27) containing said material (28) with respect to said heating means (3), the thermally conductive means (2) having an upper part (23) able to receive each crucible (27) and a lower part downwardly extending the upper part (23) and forming an appendage (24) of the upper part (23), the bottom (5) of each crucible being tapered, so as to constitute crystallization means able to bring about the crystalliaation of one end of the melted material (28) in the heating means, said heating means making it possible for the thermally conductive means (2) to pass out through the base of said heating means (3) and the appendage (24) is arranged in such a way as to modify the thermal gradient undergone by the material during the relative displacement.
2. Apparatus according to claim 1, characterized in that it comprises several crucibles (27), in that the thermally conductive means (2) comprises a cavity (29) and in that the crucibles (27) are arranged symmetrically around the cavity (29).
3. Apparatus according to either of the claims 1 and 2, characterized in that the thermally conductive means (2) and each crucible (27) are made from purified graphite.
4. Apparatus according to any one of the claims 1 to 3, characterized in that the heating means (3) comprise high frequency field windings (7).
5. Apparatus according to any one of the claims 1 to 3, characterized in that the heating means comprise Joule effect-heated resistive windings.
6. Apparatus according to any one of the claims 1 to 5, characterized in that the assembly constituted by the thermally conductive means (2). each crucible (27) and the material (28) is placed in an enclosure (6) insulating it from the outside atmosphere.
7. Apparatus according to any one of the claims 1 to 6, characterized in that it also comprises means (17, 18, 19) for circulating a chemically inert gas, so as to produce the monocrystal in a chemically inert atmosphere.
8. Application of the apparatus according to' any one of the claims 1 to 7, to the production of barium fluoride monocrystals.
EP84401103A 1983-06-06 1984-05-29 Apparatus for making a single crystal Expired EP0130865B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8309338 1983-06-06
FR8309338A FR2546912B1 (en) 1983-06-06 1983-06-06 METHOD AND DEVICE FOR PRODUCING A SINGLE CRYSTAL

Publications (2)

Publication Number Publication Date
EP0130865A1 EP0130865A1 (en) 1985-01-09
EP0130865B1 true EP0130865B1 (en) 1989-03-15

Family

ID=9289504

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84401103A Expired EP0130865B1 (en) 1983-06-06 1984-05-29 Apparatus for making a single crystal

Country Status (4)

Country Link
US (1) US4666681A (en)
EP (1) EP0130865B1 (en)
DE (1) DE3477208D1 (en)
FR (1) FR2546912B1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8173099B2 (en) 2007-12-19 2012-05-08 Saint-Gobain Ceramics & Plastics, Inc. Method of forming a porous aluminous material
US8652253B2 (en) 2007-06-06 2014-02-18 Freiberger Compound Materials Gmbh Arrangement and method for manufacturing a crystal from a melt of a raw material and single crystal

Families Citing this family (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2648065A1 (en) * 1989-06-12 1990-12-14 Solvay DEVICE FOR RECOVERING BY MELTING THE METAL CONSTITUTING A FUSE CORE
JPH0729874B2 (en) * 1989-11-04 1995-04-05 コマツ電子金属株式会社 Bridge for connecting core wires of polycrystalline silicon manufacturing equipment
US4966645A (en) * 1989-12-04 1990-10-30 At&T Bell Laboratories Crystal growth method and apparatus
US5023058A (en) * 1990-01-30 1991-06-11 Grumman Aerospace Corporation Ampoule for crystal-growing furnace
US5178719A (en) * 1991-08-20 1993-01-12 Horiba Instruments, Inc. Continuous refill crystal growth method
US5280495A (en) * 1992-02-14 1994-01-18 Ajax Magnethermic Corporation Furnace refractory extraction system and method
US5447685A (en) * 1993-09-03 1995-09-05 Medivators, Inc. Medical waste disposal apparatus and method for disposing of waste
FR2733494A1 (en) * 1995-04-28 1996-10-31 Centre Nat Rech Scient New caesium magnesium indium fluoride crystal used as scintillator or neutrino detector
FR2746176B1 (en) * 1996-03-14 1998-04-10 NON-OXIDIZING GAS INJECTION DEVICE INSIDE AN OVEN
JP3513046B2 (en) * 1998-03-31 2004-03-31 日本碍子株式会社 Single crystal manufacturing equipment
AUPR054000A0 (en) * 2000-10-04 2000-10-26 Austai Motors Designing Pty Ltd A planetary gear apparatus
US6780239B2 (en) * 2000-10-19 2004-08-24 Ricoh Company, Ltd. Crystal growth method, crystal growth apparatus, group-III nitride crystal and group-III nitride semiconductor device
US20040258496A1 (en) * 2002-04-08 2004-12-23 Marusich Troy D. High frequency tooth pass cutting device and method
US20060201412A1 (en) * 2005-03-08 2006-09-14 Christian Poetisch Method of making highly uniform low-stress single crystals with reduced scattering
DE102005010654A1 (en) * 2005-03-08 2006-09-14 Schott Ag Production of high-homogeneous, tension-poor and large volume calcium fluoride single crystal e.g. for production of lenses, prisms and optical components for deep ultraviolet photolithography, comprises cooling crystal after its breeding
CN102492993B (en) * 2006-03-24 2015-04-01 日本碍子株式会社 Process for producing a nitride single crystal and apparatus therefor
US7961938B1 (en) * 2006-06-30 2011-06-14 Adobe Systems Incorporated Finding and structuring images based on a color search
US9109299B1 (en) * 2011-03-30 2015-08-18 CapeSym, Inc. Solidification of high quality alloy semiconductors
CN104790025A (en) * 2015-04-14 2015-07-22 营口市荣兴达科技实业有限公司 Preparation device and preparation technology for magnesium fluoride single crystal coating material
DE102019208389A1 (en) * 2019-06-07 2020-12-10 Freiberger Compound Materials Gmbh Process for the production of residual stress and dislocation-free AIII-BV substrate wafers

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2214976A (en) * 1939-01-05 1940-09-17 Research Corp Apparatus for the manufacture of crystalline bodies
US3033659A (en) * 1959-04-21 1962-05-08 Gen Electric Preparation of phosphor crystals
US3139653A (en) * 1959-08-06 1964-07-07 Theodore H Orem Apparatus for the growth of preferentially oriented single crystals of metals
FR1246889A (en) * 1959-10-15 1960-11-25 Pechiney Prod Chimiques Sa Process for obtaining very pure silicon ingots
US3273969A (en) * 1963-12-05 1966-09-20 Philco Corp Apparatus for growing fluoride crystals
US3649552A (en) * 1967-03-31 1972-03-14 Hughes Aircraft Co Method for preparing high quality rare earth and alkaline earth fluoride single crystals
US3514265A (en) * 1967-04-05 1970-05-26 Us Army Method of growing strain-free single crystals
CA918247A (en) * 1970-04-28 1973-01-02 United Aircraft Corporation Single crystal casting
US3639718A (en) * 1970-06-15 1972-02-01 Little Inc A Pressure- and temperature-controlled crystal growing apparatus
FR2175594B1 (en) * 1972-03-15 1974-09-13 Radiotechnique Compelec
US4521272A (en) * 1981-01-05 1985-06-04 At&T Technologies, Inc. Method for forming and growing a single crystal of a semiconductor compound

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8652253B2 (en) 2007-06-06 2014-02-18 Freiberger Compound Materials Gmbh Arrangement and method for manufacturing a crystal from a melt of a raw material and single crystal
US9368585B2 (en) 2007-06-06 2016-06-14 Freiberger Compound Materials Gmbh Arrangement and method for manufacturing a crystal from a melt of a raw material and single crystal
US8173099B2 (en) 2007-12-19 2012-05-08 Saint-Gobain Ceramics & Plastics, Inc. Method of forming a porous aluminous material

Also Published As

Publication number Publication date
DE3477208D1 (en) 1989-04-20
FR2546912B1 (en) 1987-07-10
EP0130865A1 (en) 1985-01-09
FR2546912A1 (en) 1984-12-07
US4666681A (en) 1987-05-19

Similar Documents

Publication Publication Date Title
EP0130865B1 (en) Apparatus for making a single crystal
CA2517239C (en) Process for reloading a single-crystal or gradient solidification metal part
FR2511708A1 (en) METHOD AND APPARATUS FOR ADJUSTING THE ATMOSPHERE SURROUNDING A CRYSTALLINE GROWTH AREA
FR2510616A1 (en) APPARATUS FOR PRODUCING TUBULAR CRYSTALLINE BODIES
FR2550556A1 (en) PROCESS FOR ORIENTED SOLIDIFICATION OF MELTING METALS
EP0693865B1 (en) Induction plasma torch
FR2589489A1 (en) MONOCRYSTALLINE SILICON SUBSTRATE AND METHODS AND APPARATUS FOR MAKING SAME
FR2602503A1 (en) PROCESS AND APPARATUS FOR PURIFYING SILICON
EP0034982B1 (en) Process for preparing homogeneous films of hg1-xcdxte
FR2465802A1 (en) PROCESS FOR SOLIDIFYING A FLUID SUCH AS A SILICON BATH AND METHOD OBTAINED
EP1049820B1 (en) Method for epitaxial growth on a substrate
FR2526449A1 (en) PROCESS AND DEVICE FOR MANUFACTURING A MONOCRYSTAL, FREE FROM ANY STRESS, OF A FERROELECTRIC COMPOUND HAVING A CRYSTALLINE STRUCTURE
FR2553232A1 (en) METHOD AND DEVICE FOR PRODUCING A INGOT OF A POLYCRYSTALLINE SEMICONDUCTOR MATERIAL
FR2569430A1 (en) APPARATUS FOR EXTRACTING SINGLE CRYSTALS FROM A BATH OF MOLTEN SEMICONDUCTOR MATERIAL CONTAINED IN A CRUCIBLE
FR2570088A1 (en) APPARATUS AND METHOD FOR HORIZONTALLY GROWING CRYSTALS OF SHEET SILICON WITHOUT CRUSH
FR2502650A1 (en) APPARATUS AND METHOD FOR GROWING CRYSTALLINE CRYSTALLINE BODIES
CH389176A (en) Optical element and method for its manufacture
EP0565415B1 (en) Process for preparing an ingot of high critical temperature superconducting oxide
WO2009106625A1 (en) Method for the crystallogenesis of a material electrically conducting at the molten state
CH646402A5 (en) Method for producing and garnet gadolinium gallium.
CA1297763C (en) Process for the preparation of a cristalline ingot of
EP0775766A1 (en) Crystallisation furnace for producing material with low thermal conductivity and/or low hardness
EP1399606B1 (en) Device for producing alloy crystals
FR2800365A1 (en) PROCESS FOR OBTAINING NANOSTRUCTURES FROM COMPOUNDS HAVING A HEXAGONAL CRYSTALLINE FORM
FR2560226A1 (en) Process for the preparation of a polycrystalline alloy intended for the production of single crystals by passing through a solvent zone

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): DE GB NL

17P Request for examination filed

Effective date: 19850608

17Q First examination report despatched

Effective date: 19860516

D17Q First examination report despatched (deleted)
RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: COMMISSARIAT A L'ENERGIE ATOMIQUE

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE GB NL

REF Corresponds to:

Ref document number: 3477208

Country of ref document: DE

Date of ref document: 19890420

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19950504

Year of fee payment: 12

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19950516

Year of fee payment: 12

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19950629

Year of fee payment: 12

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19960529

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19961201

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19960529

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19970201

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 19961201